A waterjet intensifier has a high pressure cylinder of, for example, up to 40,000 psi or greater; and fluid to the high pressure cylinder is supplied via an inlet check valve that also must be capable of operating reliably at such high pressures. One example of an inlet check valve assembly is described in U.S. Pat. No. 6,021,810, which discloses an inlet valve mounted on the end of a projecting portion of a generally cylindrical check valve body. The inlet check valve has a ball valve element that is mounted over an inlet passage. Such a check valve functions well in service, however, the design does have an opportunity for an improvement. The valve body is made of a steel material that is not as hard as the ball valve. After some time in service, the repetitive action of the ball valve being pushed against the valve body seat by the high pressure liquid results in wear on the valve body where the ball valve seats. After continued use, the inlet check valve should be serviced, which requires that the valve body be machined or replaced to restore a high quality inlet valve seat. Such a servicing process is costly and labor intensive. Consequently, there is the need for an improved inlet check valve that has a longer useful life.